The invention relates to a supported catalyst containing ruthenium and palladium, to a process for the preparation of such a catalyst and to a process for the preparation of a mixture of substituted or unsubstituted cyclohexylamine and substituted or unsubstituted dicyclohexylamine by catalytic hydrogenation of substituted or unsubstituted aniline using this ruthenium catalyst.
It is known to prepare cyclohexylamine and other ring-hydrogenated amino compounds by catalytic hydrogenation of aniline and other aromatic amino compounds. The known catalysts for this reaction are: cobalt catalysts containing a basic additive (GB 969,542), Raney cobalt (JP 68/03180), ruthenium catalysts (DE-AS (German Published Specification) 1,106,319), ruthenium catalysts doped with alkali metal compounds (U.S. Pat. No. 3,636,108) or nickel catalysts (German Patent Specification No. 805,518).
The majority of the processes mentioned are carried out under pressure and mainly produce cyclohexylamine along with only a small amount of dicyclohexylamine. Dicyclohexylamine is therefore often prepared by other processes, for example by hydrogenation of diphenylamine under pressure using a ruthenium catalyst (DE-AS (German Published Specification ) 1,106,319). Furthermore, dicyclohexylamine is formed in the reaction of cyclohexanone with cyclohexylamine in the presence of a palladium/carbon catalyst at a hydrogen pressure of about 4 bar (FR 1,333,692). The process of German Patent Specification No. 805,518 mentioned is mainly aimed at the production of dicyclohexylamine, although it involves complex recycling of byproducts.
Further drawbacks of the processes mentioned are the in some cases significant amounts of cyclohexane waste product and also the short life of the catalysts used. It was therefore desired to develop a process which is useful on an industrial scale and in which the loss caused by the formation of cyclohexane are reduced and the life of the catalyst used is improved and also to develop a process in which cyclohexylamine and dicyclohexylamine are formed together in amounts which, depending on the demand of the two substances mentioned, are variable.